A flying boat is a fixed-winged seaplane with a hull, allowing it to land on water, that usually has no type of landing gear to allow operation on land. It differs from a floatplane as it uses a purpose-designed fuselage which can float, granting the aircraft buoyancy. Flying boats may be stabilized by under-wing floats or by wing-like projections (called sponsons) from the fuselage. Flying boats were some of the largest aircraft of the first half of the 20th century, exceeded in size only by bombers developed during World War II. Their advantage lay in using water instead of expensive land-based runways, making them the basis for international airlines in the interwar period. They were also commonly used for maritime patrol and air-sea rescue.
Their use gradually trailed off after World War II, partially because of the investments in airports during the war. In the 21st century, flying boats maintain a few niche uses, such as dropping water on forest fires, air transport around archipelagos, and access to undeveloped areas. Many modern seaplane variants, whether float or flying boat types, are convertible amphibious aircraft where either landing gear or flotation modes may be used to land and take off.
The Frenchman Alphonse Pénaud filed the first patent for a flying machine with a boat hull and retractable landing gear in 1876, but Austrian Wilhelm Kress is credited with building the first seaplane Drachenflieger in 1898, although its two 30 hp Daimler engines were inadequate for take-off and it later sank when one of its two floats collapsed.
On 6 June 1905 Gabriel Voisin took off and landed on the River Seine with a towed kite glider on floats. The first of his unpowered flights was 150 yards. He later built a powered floatplane in partnership with Louis Blériot, but the machine was unsuccessful.